When processing webs, it is frequently necessary to align the webs being processed with respect to some predetermined path of travel. For example, it is usually desirable to maintain the edges of webs being laminated in alignment with one another, without reducing the typically high speeds of the web-laminating process. Improper alignment may lead to excessive waste of material, and low quality and possibly useless laminated web.
Possible causes of improper alignment include, among other things, flexing of the web-laminating apparatus in operation, wandering of the web laterally with respect to its principal direction of motion along the rollers of the apparatus, and telescoping of the web on its web-supply roll, that is, the layers of the web in the roll being laterally or axially offset with respect to one another. Flexing of the apparatus has been reduced by over-designing the machinery to reduce or eliminate the flexing, although this increases the cost and weight of the machinery, and by supporting both ends of the rollers, although this makes loading the web-supply roll more difficult.
U.S. Pat. No. 3,598,332 discloses, among other things, a web-supporting roller assembly including two circular flanges adjacent opposite ends of the roller, against which a loosely wound web on the roller can be tapped to align the edges of the wound web, thereby reducing or eliminating telescoping of the web on the roller. The flanges are centered on the axis of rotation of the roller, and rotate with the roller. It is believed that the assembly is unsuitable for aligning the edges of tightly wound web, the layers of which would resist being forced into edge alignment on the roller. U.S. Pat. No. 4,322,044 discloses paper alignment and loading apparatus utilizing a leaf spring mounted at one end of a drive roll and bearing against an edge of the wound paper to, among other things, laterally position the paper.
Web alignment has also been attempted by electronic tracking of the webs and shifting the webs in response to an electronic signal generated according to the position of the web. Electronically-controlled apparatus of various types are discussed in U.S. Pat. Nos. 3,244,340; 4,068,789; 4,500,045; 4,527,069; 4,572,417; and 4,575,065. U.S. Pat. No. 3,784,076 discloses, among other things, a web guide roll having slats along its outer surface that translate in response to a signal to guide the web. Problems with such apparatus include the complexity and expense of the apparatus, and dependence on possibly unreliable electronic feedback to maintain the alignment of the webs.